1. Develop new methods for assaying allotype suppressor T cell activity and improve current methods to enable the studies outlined below. 2. Isolate (or enrich for) and characterize suppressor T cells from chronically suppressed SJL x BALB/c animals. 3. Understand the mechanism by which suppressor T cells from chronically suppressed SJL x BALB/c prevent differentiation of antibody forming cells from B cell precursors. 4. Study the induction of T cell mediated, chronic allotype suppression in SJL x BALB/c hybrids. 5. Study the genetic control of susceptibility to chronic suppression. 6. Determine relationship of allotype suppressor T cells to the normal regulation of immunoglobulin in synthesis.